Coastal and like defense unit



Jan. 4, 1944. w p 2,338,355

' COASTAL-AND LIKE DEFENSE UNIT Filed Aug. 15, 1941 Patented Jan. 4,1944 UNITED STATES PATENT OFFICE Application August 15, 1941, Serial No.407,076 In Great Britain August 23, 1940 i Claims.

This invention relates to, coastal and like defense units and isparticularly concerned with units of the general character describedinthe specification of British patent application No. 10,822 of 1940. Suchunits comprise floating hulls and are intended to be built of reinforcedconcrete or other suitable material. The shape and dimensions of theunit may embody considerable variations to obtain the necessarysteadiness. Thus for example the structure may resemble a truncated conewith the apex downwards, or may be of stepped formation including two ormore truncated cone sections or cylindrical sections of different size,or various combinations of these. The different sections may becylindrical or polygonal in plan and certain sections, more particularlythe uppermost section which lies at the water plane, may approximate toan oval shape in plan, i. e., the part or parts in question may beelongated in the horizontal direction.

An object of the present invention is to provide a unit of the abovegeneral character having an improved structural form giving thenecessary stability, and steadiness. Another object is to provide a hullform which facilitates the building of the unit and subsequentlaunching.

According to the invention a floating unit or hull, of the character andfor the purposes described, is provided with a flat, curved or domebottom surrounded by a circular or annular keel. According to a furtherfeature of the invention, the said keel may be of relatively heavyconstruction, 1. e., its thickness in cross-section may be substantiallygreater than that of the contiguous wall of the structure of which thekeel may form the lowermost part or a downward continuation. Theprovision of the keel has the dual ef fect of offering resistance torolling or angular movement in all directions, and lowering the centreof gravity of the unit, thus improving its general behaviourparticularly in disturbed water.

A further advantage of the annular keel is that it provides a footingupon which the unit may rest stably when grounded for any reason, as forexample during construction or when in dry docking. Moreover if the unitshould be grounded when in service, e. e., due to an unusually low tide,the keel will tend to assist the unit to hold firmly in its groundedposition by suction.

In some circumstances, however, the suction efiect aiforded by the keelmay not be desired and in order to meet this requirement, through-waysor passages are formed in the keel below the bottom proper of the unitat or near its junction with the shell.

According to a further feature of the invention, strengthening gussetsor webs may beprovided connecting the keel and bottom of the unit.

According to a further feature of the invention the keel may be spacedfrom the wall of the structure and connected thereto by gussets or websthat extend between the hull of the unit and the keel.

It is preferred to construct the keel of reinforced concrete integrallywith the main portion of the hull structure. The keel reinforcement willbe interconnected with the reinforcement of the walls and bottom of theunit, and/or with the reinforcement of the strengthening webs wherethese are provided.

It will be understood that while the preferred form of the keel iscircular, i. e., comprising an annulus, this may be modified so that thekeel is polygonal. The sides may be parallel or inclined to the verticalaxis of the unit.

The hull may be of stepped form.

In the accompanying drawing:

Figure 1 is an elevation, partly in section, of a stepped unit having akeel according to the invention, 1

Figure 2 is an inverted plan view of the unit showing the bottom andkeel, and

Figure 3 is a part section of a modified form in which the keel isseparated from the unit and is connected. thereto by webs or gussets.

In carrying the invention into efiect, according to one convenient mode(see Figures 1 and 2) as applied by way of example to a reinforcedconcrete unit adapted to accommodate a crew of about six to twelve men,the structure comprises a stepped hull I having a maximum diameter ofabout twenty-three feet and a total height of about twenty feet. Thehull is stepped at 2 and comprises a substantially cylindrical orprismatic upper portion 3 and a lower portion 4 of truncated conicalform joined to the upper portion by the shoulder or step 2. It will beunderstood that this feature of stepping of the hull is in no sensenecessary to the present invention.

The diameter at the base of the unit is about thirteen feet in thepresent example and the bottom 5 in shape may be convex downwards orsubstantially flat except for an inclined annular portion 6 where thebottom joins the sides. The average thickness of the hull shell andbottom may vary from about 5 inches upwards. The keel is circular inplan and forms a downward, outwardly extending continuation of the sidewall of the unit. The keel 1 may be between two and three feet in depth,and of corresponding suitable thickness, and may be thicker than thehull shell. The keel may be of downwardly tapered shape incross-section.

Any convenient number of strengthening webs, beams or gussets 8 may beprovided extending between the inner wall la of the keel and the outerinclined portions 6 of the bottom.

The upper surface of the bottom is further strengthened by the provisionof cross ribs 8 When required, through-ways or channels are providedextending from outside the keel at its junction with the bottom and theinterior of the keel between the webs. These channels may be of anyconvenient size and number. Preferably they lie closely adjacent to theunderside of the bottom.

Gussets or webs 9 are also provided in the space formed by the lowerwall 4, the step 2 and the keel I. These webs extend to the bottom ofthe keel and are of substantial depth to provide strength and resistanceto angular movement of the unit about its axis. Vertical buffer bars 9are also arranged about theouter cylindrical wall of the upper part 3.

It will be understood that while the invention has been described asapplied to a particular form of hull, it may be applied with equalfacility and advantage to other forms for example to forms approximatingto that of the cenventional buoy.

In the construction of a unit as above described, the mould for thelower part including the keel may be formed by a block secured to theerection floor or platform, and surrounded by shuttering. After theconcreting has been completed and the unit is ready for removal, somedifhculty may be experienced in separating the bottom from the mouldingblock due to suction effect. The provision of vent passages combinedwith a relieved or tapered form of the inner surface of the keel aspreviously described overcomes this difficulty, and if necessary wateror compressed air may be introduced into one or more of the saidpassages to assist in the separation. Thus the invention not onlyprovides an improved structure for use as a defense unit which possesesthe advantages in service indicated in the foregoing, but one which iseasier to build and handle.

According to a modified arrangement of keel, as applied moreparticularly to a unit in which the hull is not stepped (see Figure 3),the keel i9 is separated from the wall of the unit and comprises acircular concrete ring which may be reinforced by metal membersextending into The diameter of the keel ring may vary but convenientlythe edge Illa of the web is substantially parallel to the wall of theunit and extends downwardly to the outer surface of the keel ring. Withthis arrangement gussets of substantial height and depth are providedparticularly at the lower part adjacent the keel ring which improve thestability of the unit and provide substantial resistance to rollingand/or angular movement. With the increased diameter afforded by theseparated keel E9 the thickness may be considerably less than in theform first described above and may be less than the thickness of thewall of the hull.

I claim:

1. A floating coastal defense unit including a hull composed of an upperpart, a lower part, a lateral shoulder joining the upper and lower partstogether, the lower part being a downwardly decreasing area in crosssection, an annular keel depending and flared outwardly from the bottomof the lower part, and bracing fins respectively on the outer surfacesof the side walls of the lower art between the shoulder and the keel andbetween the keel and the bottom.

2. A floating coastal defense unit including a hull comprising an upperpart, a lower part of small diameter, a lateral shoulder portion joiningthe upper and lower parts, the lower part including a bottom having acentral fiat portion and an inclined outer portion, the walls of thelower part of the hull being tapered downwardly and joined with theinclined portion of the bottom thereof, an annular and outwardly flaredkeel depending from the bottom part of the hull, radially arrangedgussets between the inner surface of the keel and the outer surfaces ofthe inclined portions of the bottom, and a series of laterally extendingvertically arranged fins on the outer surface of the side walls of thelower part of the hull and joining the annularly inclined shoulder andthe outwardly flared keel.

3. A floating unit as claimed in claim 2, in which all of the foregoingparts are formed of concrete and arranged so as to be cast in one piece.

4. A floating unit as claimed in claim 2, in which additionalreinforcing bars are arranged in cross formation on the upper surface ofthe lower part and formed integrally therewith.

WILLIANI ARTHUR PHILLIPS.

